In general, a power supply apparatus for supplying power to a product (notebook, netbook or the like) having a self charging battery or a product (radio, CD player or the like) having no charging battery includes a connector connected to the corresponding product, a plug connected to commercial AC power and the like, and has a structure of converting the commercial AC power to DC power suitable for the corresponding product and providing the converted DC power to the product through the connector.
However, the power supply apparatus has a problem in that power is wasted since standby power is continuously generated even in a state where a power supply of the product is turned “off” or a battery is fully charged.
Due to the above problem, a program for legally regulating standby power is recently prepared all over the world including Korea. The standby power of the power supply apparatus has been restricted to 1 W from 2010 in Korea, and the standby power was restricted to 1 W or less in 2010 and a bill of restricting the standby power to 0.5 W has been passed and is due to take effect in Europe in 2013.
Accordingly, it is greatly required to provide a method of minimally maintaining or cutting off the standby power in the power supply apparatus.